1. Field of the Invention
The present invention relates to spiral-link fabrics. More specifically, the present invention relates to spiral-link fabrics having drive bars for use as conveyor belts and on other industrial machines requiring fabrics/belts.
2. Description of the Related Art
A conveyor is a mechanical system which allows for fast and efficient transport of small or bulky materials over a short defined area. There are a variety of industrial applications which require the use of conveyors. For example, in the food processing industry conveyors are used to move food items through various processing steps (e.g. from final preparation to packaging). Other uses include transporting boxed or packaged goods into or out of a warehouse. For example, transporting goods from the shelves on which they are stored to loading docks where trucks are waiting to be loaded.
A common type of conveyor comprises a conveyor belt (or fabric) in the form of an endless loop around two or more rollers (or drums). In this case, the outward surface of the conveyor belt is in contact with the goods while the inner or machine-side of the belt contacts the rollers. Conveyor belts can be formed in almost any manner including weaving machine direction (“MD”) and cross machine direction (“CD”) yams, impregnating woven or nonwoven substrates with resin, and linking plastic or metal spiral coils.
A conveyor belt may be formed completely of spiral coils (so called “spiral-link belt”) as taught by Gauthier, U.S. Pat. No. 4,567,077; which is incorporated herein by reference. In such a belt, spiral coils are connected to each other by at least one connecting pin, pintle or the like. FIG. 1 is a diagram of a prior art spiral-link belt showing the interconnections between a right-turn spiral coil 101 and a left-turn spiral coil 102. A pintle 103 is inserted between the interdigitated loops of the right and left turn spiral coils. For clarity, the foreground portions of the coils are shown as solid lines while the background portions of the loops are shown as dashed lines. Alternating spiral coils can be repeatedly linked in this manner to form a belt of almost any dimension. In theory, a seam can be placed at any location in the belt body where a connecting pin may be removed. Spiral-link belts offer a number of advantages over traditional belts. For example, the seam of a spiral-link belt is geometrically similar to the rest of the belt body. A spiral-link belt may also be coated or impregnated with a resin or polymeric material.
Conveyors may be inclined to transport goods from one height to another. As a result, unless some type of arresting means is used the goods could shift, slide, or roll on the conveyor. A variety of arresting means have been devised to overcome this problem. For example, some conveyors use belts coated with a rubber or polymeric resin material which has a high coefficient of friction and prevents goods from slipping.
Another means for preventing slippage is to attach drive bars to the conveyor belt in the cross-machine direction. The attachment of these drive bars (typically, by bonding or sewing) is often a difficult and time consuming process. Moreover, since the attached drive bars often have different characteristics than the belt and are not well integrated, the attachment means may cause localized stresses which lead to failure of the drive bar or the entire belt. As will be readily appreciated, replacing drive bars can lead to delays in using the conveyor, and also represents a significant cost to the user. Accordingly, there is a need for a conveyor belt having well integrated drive bars.